天津周边海域表层水体理化要素分布特征和水质评价

Distribution characteristics of physical and chemical elements and water quality assessment in surface water surrounding Tianjin

通过对天津周边海域表层水体的一些理化要素进行调查,得到化学需氧量(CODMn)、活性磷酸盐(PO34--P)、氨氮(NH4+-N)、亚硝酸盐氮(NO2--N)及硝酸盐氮(NO3--N)含量从离岸近的海域向外海方向递减。水温、pH值、盐度的变化趋势则正好相反;在此次调查期间,天津周边海域海水中无机氮的主要存在形式为NO3--N和NO2--N;相关性分析表明,盐度与化学需氧量、活性磷酸盐、无机氮、亚硝酸盐氮在p=0.01水平上均呈极显著负相关;活性磷酸盐与无机氮、NO2--N和NH4+-N含量均在p=0.01水平上呈极显著正相关;由N/P比和E值的平面分布图可以得到,沿岸N/P比最低,离岸越远的地方N/P比越高。E值的平面分布恰恰相反。北塘附近海域依然是富营养化最严重的区域;本调查海域主要是磷限制,无机氮仍然是此海域的首要污染因子,其次是化学需氧量。

Distribution characteristics of physical and chemical elements surrounding Tianjin was researched. The results showed that DIN, active phosphate and CODMn content reduced from the coast to offshore sea water, while the water temperature, pH and salinity were just on the contrary; During the period, the main formations for DIN were NO 3- --N and NO2 --N; The correlation analysis showed that the significant negative relationships were found between the concentration of salinity and CODMn, active phosphate, DIN, NiO2- --N; the positive relationships were found between active phosphate and DIN, NO2 --N, NH＋ --N. Level d,istribution of N/P ratio and Eutrophication index showed that N/P ratio in the coast was lower than that far ：away from the coast, while the Eutrophication index was just on the contrary. Eutrophication near Beitang was still serious. It was at the stage of phosphorus--limited potential eutrophication, and DIN was the first contamlinate factor, CODMn was secondly.